October is Space Month. At Duke University, space research is more than just science - it's a bold journey across disciplines. This is the first in a series of stories featuring innovators, dreamers and doers shaping the future of the exploration of the cosmos.
From fairy tales - such as Sleeping Beauty and Rip Van Winkle - to science fiction films, including Planet of the Apes and Alien, people have long been fascinated by the concept of humans undergoing prolonged periods of sleep.
Ana Breit's fascination started with her studies of body temperature regulation and hibernation. Her early research focused on bats, which can double their weight before entering a months-long hibernation state. A year ago, when she joined the Duke Lemur Center as a research scientist, she began studying Malagasy fat-tailed dwarf lemurs. "Being able to study hibernation in the closest relatives to humans able to hibernate is an incredible opportunity," said Breit, who, along with Duke Lemur Center colleagues, received a $30,000 NC Biotech Flash Grant to study hibernation at warmer temperatures.
While many space films have depicted humans in cryogenic tubes during long space flights, in reality, this kind of "synthetic hibernation" would lead to numerous health-related challenges, including a loss of cognitive function.
To preserve cognitive function, inducing synthetic hibernation in humans will likely require temperatures warmer than those seen in traditional cold-weather hibernation. That's where lemurs come in.
Let the Hibernating Begin
The Duke Lemur Center houses the only colony of fat-tailed dwarf lemurs within human care. All research conducted at the Lemur Center is non-invasive. It has two state-of-the-art hibernacula rooms, which each hold up to 10 hibernating lemurs and allow researchers to control the ambient temperature and mimic Madagascar's light cycles. The annual change in light cycles is a reliable signal for hibernating animals to prepare for winter. Respirometry equipment measures metabolism, while radio collars track skin temperature.
Researchers hypothesize that hibernating at warm temperatures - warm enough to maintain important homeostatic processes and cognitive function, but cool enough to save energy - is essential for the success of long-duration space exploration missions.
Hibernation by humans in space would serve several purposes: It would cut down on the amount of food or drink required, require far less oxygen since respiration during hibernation is significantly less, prevent muscle and bone deterioration, and it would cut down on boredom or loneliness during extended space voyages.
While hibernation has long been studied in rodents such as ground squirrels, no primate or tropical mammal was documented as being able to hibernate until 2004 German researchers published a study in Nature, detailing that fat-tailed dwarf lemurs spend up to seven months in tree holes hibernating. As their name suggests, these lemurs store fat in their tails, which can make up to 40 percent of their total body weight.
During hibernation, fat-tailed lemurs enter periods of energy conservation called torpor, which involves a significant reduction in metabolism, heart rate and breathing, resulting in body temperature that matches ambient temperature. These are broken up by active rewarming phases known as interbout arousals, or short temporary periods of normal metabolic levels that interrupt prolonged periods of hibernation.
"So, we know the basis of mammalian hibernation. But we need to know specifically how that will translate into humans. And dwarf lemurs are this primate, this intermediate step, to looking at how it could work in humans."
Comparing Temperatures
Like many animals that hibernate, fat-tailed lemurs do so because of a lack of available food. For them, that's during the dry season in Madagascar. At the Lemur Center, the animals will go into hibernation toward the end of October or early November, until March or April.
Breit's research compares two groups: One group experiences extreme daily temperature swings, while the other remains in a more stable environment. Hibernating mammals need to rewarm periodically. Lemurs in the room where temperatures fluctuate between 53 and 89 degrees Fahrenheit can passively rewarm each day, saving energy. Those in the stable room, where temperatures range from 64 to 71 degrees Fahrenheit, must actively rewarm, spending more energy and burning through fat reserves.
Comparing Lemur Populations
Breit is also interested in how immune function and inflammatory responses are affected by hibernation. To determine whether these and other homeostatic processes are shut down during certain points during the hibernation season, Breit is working with researchers across the country. This research will tell us whether lemurs (and potentially humans) could get sick while hibernating.
To ensure the lab-based findings reflect natural behavior, Breit's team is running a concurrent field study in Madagascar during the island's dry season. Antonin Andriamahaihavana, a PhD student at the University of Antananarivo in Madagascar, is partnering with the Duke Lemur Center to study wild dwarf lemurs in their native habitat, collecting energetic data in naturally fluctuating environments. This fieldwork helps validate the lab results and ensures the research isn't just observing the traits of hibernation of lemurs in human care.
Cognitive testing is another aspect of the study. One of Breit's collaborators, Dr. Brendan Johnson, a DLC veterinarian and primate cognition researcher, is leading memory and problem-solving testing. Lemurs are given small puzzles to solve, often motivated by a treat like half a craisin. Their performance is scored based on how many levels they complete and how quickly they solve each task. These tests are repeated after hibernation to assess changes in cognitive function. The guiding question: "After astronauts wake up, are they still able to drive the spacecraft?"
Breit's research program is building on foundational work conducted by previous Lemur Center researchers. The infrastructure, protocols and baseline data they established allowed Breit to step in and immediately begin asking high-impact questions. In the past, researchers could only measure skin temperature. Now, she can determine how much energy is spent at different temperatures and during periods of arousal.
"If they hadn't started the hibernation program here, I wouldn't be able to conduct the research that I do," said Breit. "It allows me to build off questions they've already asked. And I can add different layers to it that make it even stronger."
What began as a curiosity about body temperature has evolved into a mission to help humans sleep their way to the stars - guided by the rhythms of tropical lemurs, the precision of modern science, and the power of interdisciplinary collaboration.
